The present invention relates to a die casting machine and more particularly to a die casting machine having an improved structure in which a mold is clamped by a horizontal clamping force, a molten bath is injected vertically, and injection pressure is not adversely applied to constructional members.
Recently, an aluminum alloy die cast product has been widely utilized for strong structural parts or elements. In a die casting method for producing such an aluminum alloy die cast product with substantially no cavity, a vertical injection-type die casting machine has been utilized for the reason that a vertical injection-type die casting machine has a relatively short injection sleeve and hence has a merit of less temperature lowering of a molten bath during the injection process. Moreover, there is no fear of causing cavities due to gas in the injection sleeve, and since an injection plunger faces a cavity of a mold assembly, an injection pressure is effectively transferred. According to these advantageous points, the vertical injection-type die casting machine has been widely utilized, and more particularly, since a horizontal clamping-type machine, in which the mold is clamped by horizontal clamping force, has a good maneuverability, a horizontal clamping- and vertical injection-type die casting machine has been widely utilized.
FIG. 9 shows one example of a conventional horizontal clamping- and vertical injection-type die casting machine, which is for example disclosed in the Japanese Utility Model Publication No. 2-21168. Referring to FIG. 9, a mold assembly comprises a stationary mold half 100 and a movable mold half 101, which are horizontally clamped by the horizontal clamping- and vertical injection-type die casting machine which is equipped with an injection plunger 103 for injecting a molten bath into a cavity 102. The injection plunger 103 is accommodated in a pit 104 formed by digging in an installation bed and is swingable through a swing shaft 105. A molten bath feed gate 115 is formed to the parting surfaces of the stationary and movable mold halves 100 and 101. In each injection cycle, the injection plunger 103 is swung to feed the molten bath from a ladle to an injection sleeve 106, and the injection sleeve 106 is positionally aligned with the gate 115 and abuts thereagainst under pressure, whereby the molten bath is injected into the cavity 102 of the mold assembly.
In the horizontal clamping- and vertical injection-type die casting machine of the structure described above, since the injection pressure is applied in a direction normal to a direction of a clamping force, the stationary and movable mold halves 100 and 101 are pressed upwardly as shown in FIG. 10 and a tie bar 107 is bent, and hence the upper portions of the stationary and movable mold halves 100 and 101 are opened, resulting in a generation of burr in a mold product.
In order to obviate such defect, in the prior art, as shown in FIG. 9, a lower portion of a stationary die plate 108 is secured to a machine frame 109, and a movable die plate 110, under the mold clamped state, is provided with a securing member 111 for securing it to the machine frame 109. The movable die plate 110 is supported by the machine frame 109 so as to prevent the movable die plate 110 from being raised and bent by the injection pressure.
However, even in this improved prior art structure, it is necessary to locate the securing member 111 for securing the movable die plate 110 at the time of clamping the mold, complicating the structure for withstanding the injection pressure. Moreover, it is necessary to dig the pit 104 into the installation bed for locating the injection plunger, which makes maneuverbility and maintenance of the die casting machine itself difficult.
Furthermore, in order to solve the prior art problem described above, the same applicant provided a further improved die casting machine such as disclosed in the U.S. patent application Ser. No. 1-93349 (93349/1989) and shown in FIG. 11. Referring to FIG. 11, a die casting machine is provided with an injection plunger 203 which is secured to a injection frame 212. The injection frame 212 is inserted, to be slidable, into a guide groove 213 formed in parallel with a mold opening-closing direction at a position below stationary and movable die plates 208 and 210 so that the injection frame 212 is suspended in the groove 213. In this prior art structure, the injection pressure is received uniformly by the stationary and movable die plates 208 and 210 so as not to apply the bending moment to stationary and movable mold halves 200 and 201.
However, in the prior art structure of FIG. 11, since the injection plunger 203 is coupled to the stationary die plate 208 and the movable die plate 210 through the injection frame 212, it is necessary to perform a centering adjustment of the injection plunger 203 with respect to an injection sleeve 206 provided on parting surfaces of the stationary and movable mold halves 200 and 201 secured to the respective die plates 208 and 210. Namely, because it is required to selectively use the stationary and movable mold halves 200 and 201 having different thicknesses in accordance with differing kinds of cast products, a centering adjustment is needed between the injection plunger 203 and the injection sleeve 206 to be fitted to the parting surfaces of the mold halves 200 and 201 every time of the exchanging of the mold halves. Therefore, the construction of the die casting machine itself becomes complicated and the centering adjustment involves much time and troublesome work, thus being inconvenient even in this improved structure of the die casting machine.